Intervertebral Implant

ABSTRACT

The invention relates to an intervertebral implant comprising a spacer constituted by first and second parts ( 12, 14 ), said parts being provided with mutual assembly means comprising first clip-fastener means ( 54, 56 ) secured to one of said parts, second clip-fastener means ( 49, 50 ) secured to the other part and suitable for co-operating with the first clip-fastener means to achieve releasable clip-fastening between the two parts, and guide means for guiding the two parts ( 12, 14 ) during clip-fastening, said guide means being distinct from the clip-fastening means and comprising: 
         a substantially non-deformable first guide assembly ( 42, 44 ) secured to one of said parts; and    a substantially non-deformable second guide assembly ( 46, 48 ) secured to the other part to co-operate with the first guide assembly.

The present invention relates to an intervertebral implant for anordinary portion of the spinal column, and more particularly theinvention relates to the spacer of the implant.

Intervertebral spacers are devices that are well known for placingbetween two adjacent vertebrae in order to secure the two vertebrae toeach other so as to maintain a fixed gap between them. French patentapplication FR 01/03362 in the name of the Applicant describes suchspacers. It suffices to recall that the spacer is provided at each ofits ends with a notch in which the spinous process of a vertebra isengaged. A system of ties or braids serves to secure each end of thespacer with the spinous process.

Nevertheless, putting such a spacer into place raises certain problemsassociated with the practice of surgery. There is a ligament known asthe supraspinous ligament that interconnects the tips of all the spinousprocesses. In order to put the spacer into place, it is necessary tomove that ligament. In practice, it is detached from the two spinousprocesses concerned, and it is moved away by means of a suitablesurgical instrument. To detach the ligament from the spinous processes,a scalpel is used. Once the spacer has been put into place, the ligamentis sewn back onto the spinous processes after making a small openingtherein to receive the suture.

The major drawback of that surgical technique is that by acting on theligament in order to detach it and then move it out of the way, it isweakened mechanically. In addition, all of those actions take time,which lengthens the duration of the surgery.

To remedy that drawback, proposals have already been made forintervertebral spacers that are made up of from two distinct portions.Each portion of the spacer is put into place on either side of thesupraspinous ligament, and then by using appropriate surgicalinstruments, the two portions of the spacer are joined together. Suchtwo-portion spacers are described in particular in U.S. Pat. No.6,156,038.

Nevertheless, the two-portion spacers described in that document arerelatively difficult to use. In particular, assembling the two portionsof the spacer together in situ is relatively difficult and it is notcertain that the two parts will together form the spacer in suitablemanner.

An object of the present invention is to provide an intervertebralspacer constituted by two distinct parts that are easier for the surgeonto assemble during surgery.

To achieve this object, according to the invention, in an intervertebralimplant comprising a spacer constituted by first and second partsprovided with mutual assembly means, the implant is characterized inthat said mutual assembly means comprise:

-   -   first clip-fastener means secured to one of said parts;    -   second clip-fastener means secured to the other part, suitable        for co-operating with the first clip-fastener means to achieve        releasable clip-fastening between the two parts in a        clip-fastening direction, said first and second clip-fastening        means forming integral portions of the two parts; and    -   guide means for guiding the two parts during clip-fastening,        said guide means being distinct from the clip-fastener means and        comprising:    -   a substantially non-deformable first guide assembly secured to        one of said parts; and    -   a substantially non-deformable second guide assembly secured to        the other part to co-operate with the first guide assembly so as        to provide mutual guidance of the two parts along said        clip-fastening direction and provide relative positioning of the        two parts in a plane orthogonal to the clip-fastening direction.

It will be understood that because each part constituting theintervertebral spacer includes firstly guide means and secondlyclip-fastener means, the guide means guarantee accurate relativepositioning of the clip-fastener means in a manner that is easy for thesurgeon. This ensures that the two parts constituting the spacer areproperly assembled together, and furthermore, that this operation can beimplemented more quickly than with the spacers of the prior art.

In addition, since the clip-fastener means form integral portions of thetwo parts, the implant is made easier for the surgeon to put into place.

In a preferred embodiment of the invention, each part of the spacer hasan assembly face that is to be pressed against the assembly face of theother part when the two parts are assembled together.

Also preferably, the guide means are constituted respectively by twoguide studs projecting from one of the assembly faces and by tworecesses opening out into the assembly face of the other part. It isthus possible to obtain effective guidance of one of the parts relativeto the other by giving the guide studs an appropriate shape.

Other characteristics and advantages of the invention appear better onreading the following description of an embodiment of the inventiongiven by way of non-limiting example. The description refers to theaccompanying figures, in which:

FIG. 1 is an exploded view of the various elements constituting theintervertebral implant;

FIG. 2 is an assembly face view showing one of the two partsconstituting the intervertebral spacer;

FIG. 3 is a side view of the spacer after the two parts constituting ithave been assembled together; and

FIG. 4 is a longitudinal section of the self-locking element used forsecuring the braids of the implant.

FIG. 1 shows the two parts 12 and 14 which are being assembled togetherserve to produce the intervertebral spacer 10. In the figure, there canalso be seen a removable element 16 used for fastening purposes and forclamping braids that serve to secure two spinous processes to thespacer. The fastener element 16 is described below. The part 12constitutes a first side piece of the intervertebral spacer. This part12 has an inside face 12 a and an outside face 12 b. The inside face 12a defines a top bearing surface 20, a bottom bearing surface 22, and amiddle assembly face 24.

The second part 14 also constitutes a side piece presenting an insideface 26 a facing towards the inside face 12 a of the part 12, and anoutside face 26 b. The inside face 26 a of the side piece 26 defines atop bearing surface 28 and a bottom bearing surface 30. In the middleregion of the inside face of the side piece 26, the part 14 has aprojection 32 that projects from the central portion of the face 26 a.This projection 32 or space-defining part defines two bearing surfaces,a top surface 34 and a bottom surface 36, these two faces beingsubstantially parallel. The space-defining part 32 may includetransverse recesses such as 38 for imparting a degree of resilience tothis portion of the spacer. The free end of the space-defining part 32defines an assembly face 40 for bearing against the assembly face 24 ofthe part 12 when the two parts constituting the spacer are assembledtogether.

In the assembly faces 40 and 24 of the two parts, there are providedmutual guidance means that act as these two parts move towards eachother in order to secure them one to the other. Preferably, the guidancemeans are constituted by two guide studs 42 and 44 projecting from theassembly face 40 of the part 14 and by two blind recesses 46 and 48formed in the assembly face 24 of the part 12. It would not go beyondthe invention if only one stud were to be provided together with onlyone recess. Preferably, and in conventional manner, the ends of theassembly studs 42 and 44 are conical in order to provide initialpositioning of the two parts. The parts 12 and 14 are secured to eachother by clip-fastener means formed respectively in the side faces 12 cand 12 d of the part 12 and in the side faces 32 a and 32 b of theprojection 32 of the part 14. By way of example, for the part 12 theseclip-fastener means consist of two pairs of cylindrical pegs 49 and 50and of two side walls projecting beyond the assembly face 44 of the part14, given respective references 51 and 52. Each side wall is providedwith two openings 54 and 56 suitable for receiving the pegs 49 and 50during clip-fastening. Each opening 54, 56 includes a deformable nib 58or 60. As also shown in FIG. 1, the pegs 49 and 50 project into a recess60 formed in the side faces 12 c, 12 d of the part 12. It shouldnaturally be added that the guide studs 42 and 44 are of a length thatis longer than that of the side walls 51 and 52 defining the femaleclip-fastener elements. Whatever the particular implementation of theclip-fastener means, they should form integral portions respectively ofthe two parts 12 and 14.

As shown more clearly in FIG. 3, when the parts 12 and 14 are assembledtogether, in the manner explained below, an intervertebral spacer isobtained having the usual structure. In particular, the bearing faces20, 22 of the part 12 and the bearing faces 28, 30 of the side piece 26of the part 14, and finally the top and bottom faces 34 and 36 of theextension 32 define two recesses 62 and 64 for receiving the spinousprocesses of the two vertebrae between which the spacer is placed.

Naturally, it should be added that the guide studs 42 and 44 are of alength that is greater than that of the side walls 51 and 52 definingthe female clip-fastener elements.

The above-described spacer is used as follows. The surgeon puts thespacer-constituting parts 12 and 14 into place, going round thesupraspinal ligament. Using appropriate surgical instruments, the twoparts are moved towards each other so as to cause the guide studs 42 and44 to co-operate with the guide recesses 46 and 48. When the resultingrelative positioning is achieved, the clip-fastener members 48, 50 and54, 56 face one another in pairs. It then suffices for the surgeon toexert pressure on the outside faces of the two parts in order to causethe parts 12 and 14 to clip together, thus obtaining the complete spacer10. It should be added that the clip-fastener elements 48, 50 and 54, 56are made in such a manner as to ensure effective fastening, while stillmaking it possible for them to be separated in the event of it beingnecessary to change the spacer. As explained above, it is easy to putthe spacer into place since it comprises only two parts.

With reference now to FIGS. 1 and 4, there follows a description of apreferred embodiment of the means for securing the spacer 10 to thespinous processes of the vertebrae. This system is constituted by thelocking or fastener part 16 and by two braids T1 and T2. The fastenerpart 16 can be secured to the outside face 26 b of the part 14 byclip-fastener means 80, 82, 84, and 86 that are identical to theclip-fastener means of the parts 12 and 14.

The fastener part 16 presents a clip-fastener face 16 b on the part 14and an outside face 16 a. The fastener part 16 presents a plane ofsymmetry P, P′ orthogonal to the faces 16 a and 16 b and parallel to thefaces 32 and 34 of the extension 30 of the part 14. The locking part 16has a central slot 90 that opens out into both faces of the part 16, andtwo symmetrical inclined side slots 92 and 94 that also open out intoboth faces of the part 16. The clip-fastener face 16 b of the part 16presents two setback surfaces 96 and 98 that extend respectively betweenthe side slots 92 and 94 and the top and bottom ends of the part 16which constitutes braid clamping surfaces. The slot 92 and the setbacksurface 98 define a first sharp edge 100. Similarly, the slot 92 and theoutside face 16 a of the part 16 define a second sharp edge 102 that isparallel to the edge 100. As shown in the figure, the edge 102 isfurther away from the midplane P, P′ than is the edge 100. In addition,it should be specified that the clamping surfaces 96 and 98 are disposedin such a manner that when the part 16 is clipped onto the spacer, thedistance between the face 26 b of the spacer and the surface 96 or 98 isslightly less than twice the thickness of the braids T1 and T2.

Each braid T1 and T2 has a first end A that is secured to the part 12.To do this, in the example described, the part 12 is provided with a topslot 104 and a bottom slot 106 in which the ends A of the braid can forma loop. After this loop has been stitched together, the braids Ti and T2are effectively secured to each end of the part 12. The braid T2 isengaged between the surface 98 and the face 26 b of the spacer and thenin the central slot 90. Thereafter, it passes over a portion of theoutside face 16 a of the part 16 and penetrates into the slot 62,passing over the edge 102. Thereafter, the braid T2 is engaged under thepresser surface 98, between the first strand of the same braid and saidsurface. When the surgeon exerts traction on the end B of the braid T2,that serves to clamp the braid T2 against the spinous process of theupper or lower vertebra. The braid T1 is naturally engaged in the part16 in the same manner in order to provide a connection with the spinousprocess of the other vertebra.

It will be understood that the fastener part 16 act for each of thebraids as a self-locking system. When the surgeon exerts traction on thefree end B of the braid, it can move without excessive friction in theslots 90 and 92 until the desired clamping effect is obtained. Incontrast, when no traction is exerted on the end B of the braid, i.e.when the intervertebral implant is in normal use, a self-locking effectis obtained by the presence of the sharp edges 100 and 102 and theclamping effect of the presser surface 98 on the two strands of thebraid.

In a preferred embodiment, the first clip-fastener means comprise atleast two male clip-fastener members 54 and 56 that are substantiallyundeformable, being disposed on either side of the assembly surface 24,and second clip-fastener means comprising at least two clip-fastenerfemale members 49 and 50 that are elastically deformable and disposed oneither side of the assembly surface 40.

Also preferably, said first guide assembly comprises at least one guidestud 42 and 44 projecting from an assembly face 40 of one of the partsand at least one recess 46 and 48 opening out into the assembly face 24of the other part.

1-7. (canceled)
 8. An intervertebral implant comprising a spacerconstituted by first and second parts, said parts being provided withmutual assembly means, said mutual assembly means comprising: firstclip-fastener means secured to one of said parts; second clip-fastenermeans secured to the other part for co-operating with the firstclip-fastener means to achieve releasable clip-fastening between the twoparts in a clip-fastening direction, said first and secondclip-fastening means forming integral portions of the two parts; andguide means for guiding the two parts during clip-fastening, said guidemeans being distinct from the clip-fastener means and comprising: asubstantially non-deformable first guide assembly secured to one of saidparts; and a substantially non-deformable second guide assembly securedto the other part to co-operate with the first guide assembly so as toprovide mutual guidance of the two parts along said clip-fasteningdirection and provide relative positioning of the two parts in a planeorthogonal to the clip-fastening direction.
 9. An intervertebral implantaccording to claim 8, wherein each of said two parts has an assemblyface, said assembly faces being pressed one against the other when theparts are assembled together.
 10. An intervertebral implant according toclaim 9, wherein the first clip-fastener means comprise at least twosubstantially non-deformable male clip-fastener members disposed oneither side of the assembly surface, and second clip-fastener meanscomprising at least two elastically deformable female clip-fastenermembers disposed on either side of the assembly surface.
 11. Anintervertebral implant according to claim 9, wherein said guide assemblycomprises at least one guide stud projecting from an assembly face ofone of the parts, and at least one recess opening out into the assemblyface of the other part.
 12. An intervertebral implant according to claim9, wherein said first guide assembly comprises two guide studs and thesecond guide assembly comprises two recesses.
 13. An intervertebralimplant according to claim 9, wherein each of said parts includes twoclip-fastener means.
 14. An implant according to claim 9, wherein thefirst of said two parts has an outside face opposite to the assemblyface, and wherein it further comprises: two braids for fastening saidspacer on two spinous processes; and a self-locking element comprisingfastener means on the outside face of one of said part; each braidhaving a first end secured to said part not associated with theself-locking element, and a second end that is engageable in saidself-locking element.